Method for replacing worn or fractured teeth on large gear rings



April 5, 1966 c. J. ROYERy 3,243,874

METHOD FOR REPLACING WORN OR FRACTURED TEETH 0N LARGE GEAR RINGS 5 Sheets-Sheet 1 Filed Aug. 2l, 1964 Fica-i o 6 7 Mw w m n ff. Ik 6 /7 E y s y @f1 Y Ihw.

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INVENTOR. @LADY d., Pore-Q c. J. ROYER 3,243,874 METHOD FOR REPLACING WORN OR FRACTURED TEETH April 5, 1966 ON LARGE GEAR RINGS 3 Sheets-Sheet 2 Filed Aug. 21, 1964 j; [5b I 7 lh.

INVENTOR. CLAD Y d. Q0 f5-Q A rroQA/E-Ys Aprxl 5, 1966 c. J. ROYER 3,243,874

METHOD FOR REPLACING WORN OR FRACTURED TEETH ON LARGE GEAR RINGS Filed Aug. 2l, 1964 .'5 Sheets-Sheet 5 INVENTOR. CLA/JY d. @onf-Q United States Patent() 3,243,874 METHOD FOR REPLACIN G WORN GR FRAC- T URED TEETH ON LARGE GEAR RWGS Clady J. Royer, 2645 NW. 26th St., Oklahoma City, Okla. Filed Aug. 21, 1964, Ser. No. 391,162 8 Claims. (Cl. 29-401) This invention relates to a method for replacing worn or fractured teeth on vlarge gear rings or gear circles. More particularly, the present invention relates to a method for quickly and easily replacing a plurality of the teeth used in a gear circle of the specific type employed in largev graders and other earth-moving equipment.

In earthmoving vehicular equipment of the type typified by the road grader manufactured by the Caterpillar Company of Peoria, Illinois, the vehicle is generally provided with alarg'e "grader blade which extends transve-rsely across and beneath the frame of the vehicle, and

is secured to a large ring gear or a gear circle of some` are generally right angularly shaped structures having a.

toe portion which extends beneath, and supports in a generally horizontal plane, the gear circle, and also having a vertically extending portion which acts as a guide to assist in maintaining the position of the gear circle relative to a vertical axis passing through the center thereof. The teeth of the gear circle extend radially inwardly toward the vertical axis of the circle and contact the upper surface of the horizontally extending. toe portion of the circle guide shoes. The vertically` extending, radially inner edges of the teeth of the gear circle frequently bear against, or come in Contact with, the `ver tically extending portions of the guide shoes so that some wear results at the vertically extending, radially inner edges of the teeth during operation of the earthmoving vehicle.

The large gear circle used in vehicles of the type described is usually further characterized in having a downwardly rextending circumferential flange formed on the outer periphery thereof and a right angular or L-shaped brace which is welded at the edge of a horizontally extending leg thereof to the lower edge of the downwardly extending circumferential flange, and at the upper edge of the upwardly extending leg thereof to the lower sur.-

face of the gear circle. The function of the L-shaped brace is to enhance the structural strength and mechanical rigidity of the gear circle.

In the operation of earthmoving vehicles of the type described, very large mechanical loads are frequently imposed upon the grader blade and transmitted through the moldboard and other connecting structure to the gear circle. These loads are frequently unevenly distributed along the blade with theresult that unequal stresses are transmitted through the moldboard and connecting structure to the gear circle, and ultimately to the gear teeth of the circle. The sudden impact imparted to the blade when it strikes buried rock or other impacted, relatively difculty moved structure also severely stresses the gear circle teeth. The loading of the teeth as thus imposed, coupled with the frictional wear and abrasion produced by the constant Wear of the teeth against the supporting and guiding surfaces, of the circle guide shoes results in 3,243,874 Patented Apr. 5, 1966" "ice life of the remaining gear circle structurey so that it his. more desirable to replace only the wornl or fractured teeth, rather than replacing the entire vgear circle.,

Another problem which arises from' the' uneven distribution of loads imposed on the gear circle during gradi' ing operations is that the gear circle will ultimately be-f, come distorted from its trueiround configuration to'aL slightly elliptical or oval configuration. This distortion' 0f the gear vcircle results from 'thev propensity of grader operators to incline the grader blade at thel same anglewith respect to the frame of the vehicle during all 'grad-'I ing operations sothat a continuous load is imposed ony one segment of the gear 'circle tending to distort the circlef` in the same direction'.

The desirability or need for replacing worn or lost teeth on various types of annular structures, such as cogs, sprockets and gears, as opposed to replacing the entire or complete gear, exists in many types of mechanical strnctures, and various methods for accomplishing vsuch re-V placement have been previously proposed and carried out with varying degrees of success. Where the structure` comprises an annular member supported on 'spokes or `a spider extending radially from a hub, it has been proposed to make the tooth-carryingannular member in segments which can be detachably secured to the spokes or spider and individually replaced when required. This procedure, which is typified by the disclosures of rShores U.S. Patent 2,285,225; Melone U.S. Patent 3,111,859 and Dawe et al. U.S. Patent 3,083,585, has the advantage of permitting only a portion V4of the entire sprocket or gear combination to be replaced when the teeth become worn, but is limited to use in structures having some type ofV radia-l support, such 'as spokes or' the like, for the annular segments. Moreover, in replacing an entire annular segment, including notonly the teeth which it is desired jto the spokes cannot be employed. Instead, the* older and- Well-known method of tooth replacement 'is employedy in which the individual worn-or fractured teeth are in'-v Thisl dividually removed andl painstakingly replaced. procedure, one form of Vwhich is described in U.S. Patent 1,406,110 to Troutner is time-consuming and expensive, and requires the employment of a highly skilled Welder. Even using Welders -of high skill, it is frequently very diflcult to procure the desired alignment and geometric relationship between the replacement teeth and those which have not been replaced.

Thef'pres'ent invention contemplates a novel method for replacing the kworn or fractured teeth on a gear circle of the .type used in large earthmoving or grader type ve-` hicles. As previously described, these vehicles have a large grader blade extending transversely across the vehicle beneath the frame thereof and supported by a large circular gear ring having radially inwardly projecting teeth. These teeth are engaged by a pinion for driving the gear circle in rotation to adjust the angular position of the grader blade. The invention is specifically applicable to wheeled graders of the type having a grader blade mounted on or suspended beneath a large metallic gear ring or circle, which gear circle is supported and guided by a plurality of guide shoes which bear against the teeth of the gear circle and. function to support the gear circle and maintain it in a position for meshing with the driving pinion.

The invention is particularly useful and applicable to gear. circles of the described type which have been distorted from' their true circular configuration by long usage in' grader vehicles in which the grader blade has been continuously extended at substantially the same angle.

Broadly described, the present invention comprises initially forming a plurality of toothed segments which areidentical in geometric configuration to corresponding arcuate segments of the gear circle upon which are located the worn or defective teeth to be replaced, as such arcuate segments were configured at the time the gear circle was new. In other words, the toothed segments which are initially formed in the practice of the present invention are segments of a true circle, and the teethwhich are carried by these segments are identical in geometric'configuration to the unworn ornew teeth which were carried by the gear circle prior to wear and deterioration of the teeth. The angular size of the toothed segments which are formed may be varied, but is preferably equivalent to an oetant of the gear circle, or 45 of are. It is very desirable to limit the size of the segments to 45 of arc or smaller since the segments are formed b'y casting, and it is difiicult and expensive to cast them in the proper configuration if they are made of larger size than `the 45 of arc for use in the larger gear circles to which the present invention is applicable.

In the. next step ofy the procedure, the preformed toothed segments are fitted in end-to-end annular relation so that a perfect circle is formed, and the ends of the segments are then secured to each other. It should be pointed out that the preformed segments which are joined in a circular configuration are of less transverse width than the overall transverse width of the gear circle which is to be reconditioned, and, as will be hereinafter pointed out, an important aspect of the invention is the saving and re-use of a substantial portion of the original gear circle as the defective teeth thereon are replaced.

In the next step of the procedure of the invention, the preformedsegments which have been joined in an annular configuration are placed on top of the gear circle carrying the defective teeth and are used as a guide for cutting away the teeth of the old gear circle, along with a portion ofthe gear circle which forms the root or base of the teeth. Alternatively, the joined segments may be superimposed on the old gear circle and a line drawn around the outer periphery of the joined segments, which line may then be used as a guide for cutting away the old teeth and their root or base structure, using a cutting torch or other suitable cutting device. By either procedure, an accurate circular guiding technique is provided which enables a Welder of average skill to perform the removal of the old teeth and their root structure from the gear circle in a fashion which will permit the preformed segments to be joined to the remaining portion of the gear circle accurately and precisely as hereinafter described. In other words, by this guiding and cutting procedure, a certain minimum portion of the gear circle which carries the teeth thereof is easily removed, with the line of severance of the removed portion from the remainder. of the gear. circle corresponding precisely to the outer peripheral surface of the joined, preformed segments which carry the new teeth so as to assure. that.

the preformed seUments can be used to replace the removed portions of the gear circle with a precise fit requiring no adjustment and a minimum amount of welding or other securement procedure.

After the old teeth and root or base structure of the gear circle have been removed in the manner described, the preformed segments which are joined in an annular configuration are fitted to the inner periphery of the modified gear circle with their outerA periphery abuttingthe gear circle inner peripheral surface formed by` the cutting operation. The new preformed segments carrying the perfectly formed teeth on the inner periphery thereof are then joined to the base structure of the original gear circle. Because of the .fact that the joined segments-.have been formed in a perfectly round configuration, the inner periphery ofthe rebuilt gear circle is now perfectly round and carries new teeth which are not fractured or worn. Moreover, the procedure lends itself to the use of harder and more exotic metal in casting the new teeth on the preformed segments than the type of metal which is used in the gear circle as originally fabricated. Thus, teeth having a longer service life are actually incorporated in the rebuilt gear circle. Moreover, in incorporating the perfectly round segmented pre formed structure within the outer peripheral base strucJ ture of the original gear circle, the distorted outer peripheral portion of the gear circle is maintained in this' form and therefore tends to resist further distortion. In other words, the. distorting influence of Yuneven loading on the grader blade has been previously imparted to that portion of the gear circle which sustains the greatest portion of the mechanical loading, and in retaining this distorted portion in the rebuilt gear circle, no further distortion tends to occur, and yet the inner periphery which carries the new teeth is in perfect round and tends to remain that way for the remaining service life' of the gear circle. l

From the foregoing description of the invention, it wil have become apparent that a major object of this invention is to provide a new and improved method for quickly and inexpensively replacing Worn or fractured teeth on gear circles of the type used in earthrnoving vehicles for supporting the moldboard of grader blades mounted on said vehicles.

Another object of the present invention is to provide a method for replacing the teeth on large gear circles 0f.

-the type described without the necessity for remov'ingthe individual teeth, and then replacing them by a buildmg' up process.

Another object of the present invention is to provide a method for replacing the teeth on large ygear circles of the type described without the necessity :for using `a jig to assure that portions of the gear circle removed by a cutting torch are removed along a precisely defined line as desired.

Yet another object of the present invention is to prof vide an improved method lfor simult-aneously replacing a plurality of Worn or fractured teeth in a gear circle of .the type used in earthmoving vehicles carrying large grader blades extending transversely of the vehicle, and beneath the frame thereof, which method can Ibe quickly and easily performed lby la welder of average skill in a manner so that the replacement teeth are penfectly shaped and are in perfect annular alignment.

An additional object of the present invent-ion is to provide a method for replacing worn teeth on -the inner periphery of a large gear circle of the type used in earth moving vehicles carrying large grader blades which ex. tend transversely of the vehicle and beneath the frame.y

thereof, which method facilitates the replacement of the, worn teeth with teeth which are constructed of harderand more mechanically desirable types of metal thanL the We.thffriginally` used in such gear circles".

Yet another object of the present invention is to provide a method for Ireplacing `worn or fractured teeth in large gear circles ofthe type used on motor graders, which method permits an out of round or distorted condition of such gear circles to be compensated, and the replacement teeth incorporated thereon to be positioned around .the periphery of a perfect circle.

Ano-ther object of the -present invention is to provide a method for replacing the teeth located at the inner periphery of a large gear circle of the .type used on motor graders, with such method tending to prevent subsequent distortion of the tooth-bearing portion of the gear circle from a true circular conliguration.

'In addition -to the foregoing-describedA objects and advantages, other vobjects Iand advantages will become apparent as the following detailed description of the invention is read -in conjunction with a perusal of the accom- `panying drawings which illustrate the invention.

In the drawings:

FIGURE 1 is a perspective view showing the manner in which gear circles of the type Ato which the present invention is applicable Iare mounted upon one type of a large earthmoving vehicle.

FIGURE 2 is a sectional view illustrating the manner in which the ygear circle is supported by one of the circle guide -shoes of the vehicle.

FIGURE 3 is a perspective view of one of the preformed lsegments used yin the practice of the present invention as such vseg-ment is ttedzto a joining jig used in the practice of the invention.

yFIGURE 4 is a plan view of the rannular structure formed lby joining in end-to-end relation eight segments of the type illustrated in FIGURE 3 and using the jig illustrated-in FIGURE E3 -for aligning the segments in endto-end annular relation.

FIGURE 5 is a view in section taken along line 5-5 of FIGURE 4.

FIGURE 6 is a perspective view of the gear circle illustrating the appearance of the Ygear circle after .the inner peripheral portion thereof has been cut away in accordance with the practice of ythe present invention.

FIGURE 7 is a View in .section taken alongf line 747 of FIGURE 6.

FIGURES is a perspective view illustrating the manner in which the annular toothed member Villustrated in FIGURE 4 is clamped to the inner periphery of the cutaway gear circle illustrated in FIGURE 6 preparatory to welding the preformed annular toothed structure to such cutaway gear circle.

FIGURE 9 is atransverse lsectional View taken through the center of the rebuilt gear circle as the gear circle is in contact with and supported by one of the circle guide shoes similar to `that illustrated in FIGURE'Z.

Referring `to the drawings in detail, and Iparticularly to FIGURE l, the specilic type of ring gear or gear circle to which the invention can most beneficially be applied is of the type which is typically mounted upon a large grader, such as that partially illustrated in FIGURE l. Graders of this type include a heavy framework 10 which is supportedon a plurality of ground engaging wheels 12 and ifrom which is suspended, by means of a drawbar 14, a large gear circle designated generally by reference character .16. The gear circle .16, which includes a iiat annular metallic member 17, is supported by a plurality of circle guide Yshoes 18 which serve to support the gear circle, and .to guide and maintain 'its ailgnment about a vertical Vaxis passing through the center thereof. The gear circle 16 is provided with a pair of downwardly depending moldboard support structures 20 which provide structure for mounting a grader blade 22. At the inner per-iphery of the annular metallic member 17, a plurality of radially inwardly extending equisized teeth 24 are providedand are positioned ,for meshing engagemen-t with a pinion gear (not seen) which is journaled in a bearing 26 carried in the drawbar trame 14.

The `manner lin which the gear circle v16 is supported and guided by the circle guide shoes y18 can best be understood by referring toFIGURE 2. As shown in FIGURE 2, the guide lshoes 18 are each generally right angularly shaped structures having van annular toe portion.

30 which extends beneath and supports the teeth 24, and

a vertically extending portion 3 2 which bears against the inner face of the gear teeth 24 and limits radially inward movement of the gear circle 16.

The gear circle 16 is further characterized in having a downwardly extending circumferential ange 33 securedV to the outer peripheral edge of the annular metallic member 17. The flange 33 is welded or otherwise suitably secured adjacent its lower edge to the horizontally extending leg 34 of an L-shaped brace designated generally by reference character 36. The L-shaped brace also includes an upwardlyextending leg 38 which Vis secured to the under side of the annular metallic member 17 at a position relatively close to the tooth-carrying peripheral edge of the member 17. In typical construction `of this type .of gear circle, the radially inner side of the L-shaped brace 36 extends in substantially the same plane as is occupied by the line at which a slight break in the upper horizontal surfacexof the annular metallic member I7 occurs, asV

shown at the point on the FIGURE 2 sectional View which is vrepresented by reference numeral 40. The line along which the base of each of the gear teeth 24 terminates is represented by the line 44 in FIGURE 2. It is to` be understood that though the brace 36 has been described as L-shaped in referring to the sectional view of FIGURE 2, this conguration represents the shape of the brace only in transverse cross-section, and the brace in its entirety is actually anv annular member having ahorizontally extending leg 34 and a vertically or upwardly extending leg .33. Thus, rthe line of intersection between the inner face of the leg 38 of brace 36 and the under Isurface of the annular metallic member 17 is actually an arcuate line which is positioned intermediate the inner and outer peripheries of themember 17. The same annular configuration characterizes the imaginaryv line 44 and the breakpoint 4@ in the upper surface of they horizontal porti-on of the gear circle 16.

Under the conditi-ons giving rise to the use of the present invention, one or more of the gearteeth 2,4 may become severely worn to the point where the teeth do not mesh well with the driving pinion, or do not ride smoothly over the circle guide shoes 18.` In m-ost instances, wearingwill be pronounced over a certain localized area of the gear circle and `will involve a plurality of theteeth in that area. Occasionally, one or more of the teeth inthe area of greatest wearmay become fractured or sheared off between the point-of the tooth and the root or base structure constituted by member 17. `When such wear and fracturing has progressed to an undesirable extent, it then becomes necessary to removethe worn teeth and replace them with new teeth by a building-up welding process or by some other method. The methods employed in the past have been time-consuming and expensive by reason of requiring a highly skilled Welder and of a'particular technique which may, in some instances, require the use of a welding jig. In many instances, it has been preferable to simply replace the entire. gear circle witha new gear circle rather than to undertake to remove the Worn teeth.

At the time in the service life of a gear circle when the gear teeth have become worn .to the extent described and possibly fractured, the gear circle as awhole has usually become distorted from its true circular configuration as originally constructed by reason ofthe high and uneven mechanical loads imposed thereon in continuous useas hereinbefore described. For example, if the grader blade 2.2 is canted at an angle of about 60 lwith respect Vtothe longitudinal axis of the frame of the 4grader vehicle andis continuously used at that angle for grading roads, the loading on the gear circle will be distributed unevenly and a distorting force will continually act on the gear circle to change its configuration to a slightly elliptical or eggshaped form. It will be seen that distortion of the gear circle 16 from a true circular configuration will tend to aggravate and further the wear of the teeth 24 carried thereby since they will then bind more severely on the circle guide shoes 13 as the gear circle is driven in rotation.

In the practice of the present invention, the gear circle 16 carrying the worn teeth 24 is initially removed from the earthmoving vehicle by techniques well understood in the art. A plurality of preformed, toothed arcuate segments are then made by casting. A typical embodiment of such preformed segments is illustrated in FIGURE 3 and is designated by reference character 50. The inner periphery of each of the preformed segments 50 carries teeth 52 which are identical in geometric configuration and circumferential spacing to the teeth 24 provided on the gearrcircle 16. The arcuate outer peripheral edge 53 of the segments 50 is formed'on a radius of curvature which is less than the radius of curvature of the break 40 in the annular metallic member 17 of the gear circle 16. Stated differently, the outer peripheral edge 53 of the segments 5) is formed on a ligure of revolution which lies somewhere between the base of the teeth 24 (or line 44)"and the upwardly extending leg 38 of the brace 36.I Dimensioning the segments 50 in this way assures that they may be easily joined to the gear circle 16 after a portion thereof has been -removed in the manner hereinafter described, even though the gear circle may be substantially distorted from its original true circular configuration.

The transverse cross-sectional configuration of the segments is best illustrated in FIGURE 5. The teeth 52 are 'thus seen to project from a root or base portion 54 which metals of greater hardness and improved durability can be used for forming the segments and their associated teeth 52 than are generally employed in fabricating the entire gear circle 16 originally. The number of the segments 50 formed, and the arcuate length of the segments, may be varied, but preferably, as hereinbefore indicated, correspond to an octant of the gear circle which is to be rebuilt. The selection of an octant, or 45 of arc, as the lineal dimension of the segments G is based upon the usual number of 64 teeth which is provided on fthe gear circles of.

motor gradersa number evenly divisible by S-and also upon the fact that if the segments are made larger than Yan octant, casting of the segments as a true segment of a circle with the teeth perfectly formed becomes quite dificult and more expensive.

After the segments 50 have been cast in the contiguration and dimensions described, they are placed on a circular jig designated by reference character 60 and illustrated in FIGURE 3. The jig 60 includes a horizontally extending annular plate 62 and a vertically extending annular retaining plate 64. Suitable legs or other supporting structure 66 may be used to support the horizontal and vertical plates 62 and 64 on the ground or on the floor of a Shop. The segments 50 are placed in endto-end relation around the jig 60 and are supported thereon by the horizontal annular plate 62. While the jig 6G is made in a true circular configuration, it is preferable to make such measurements as are necessary to assure that the toothed annular structure formed by the segments Si) is perfectly circular in shape prior to joining the ends of the segments' in end-to-end relation. After placing the segments in a true circular configuration, the adjoin- `removed from the earthmoving vehicle.

ing abutting ends of the segments are welded to each other to form the annular structure 82 illustrated in FIGURE 4 of the drawings. This structure will correspond, if it has been properly formed, to the inner peripheral portion of the original gear circle 16 as it was shaped before the teeth 24 of the gear circle became worn or fractured, and before the gear circle became distorted from its true circular configuration by evtended usage.

In the next step of the process of the present invention, the annular structure 82 illustrated in FIGURE 4 of the drawings which is formed by joining the plurality of arcuate segments in end-to-end Yrelation is superim posed or rested upon'the upper surface of the annular metallic member 17 of the gear circle 16 which has been The annular structure 82 of joined preformed segments 50 is adjusted in its position ou the upper surface of the annular metallic member 17 so that its outer periphery 60 lies at all points radially inwardly of the break 40 in the upper surface of the annular metallic member 17, and thus inwardly of the upwardly extending leg 38 of the brace 36. This type of positioning will usually not result in Acoincident alignment of all of the teeth 52 on the annular member 82 of FIGURE 4 with the teeth 24 on the gear circle 16 since the gear circle has become distorted from its circular configuration in use.

With the annular structure 82 positioned as described, one of two alternate procedures may be followed. In one of-these, a suitable line, such as a chalk line, may be drawn around the outer periphery 60 of the annular structure 82 on the upper surface of the annular metallic member 17, and the line used as a guide line for subsequently removing the inner peripheral portion of the annular metallic member 17 andthe teeth 24 attached thereto. Alternatively, the annular structure 82 'may be left in position on the upper surface of the annular metallic member 17 and the outer periphery 60 of the annular structure used as a guide for cutting through the annular metallic member 17 with a cutting torch. In either event, the removal of the inner peripheral portion of the annular metallic member 17 may be accomplished by a Welder of ordinary skill and no special cutting jig or inordinate skill on the part of the welder is required.

When the annular metallic member 17 has been cut ,through along a vertical line in the manner described,

the inner peripheral portion which carries the teeth 52 is removed from the remainder of the gear circle and the gear circle then appears as illustrated in FIGURE 6. It will be noted in referring to FIGURE 6 that some portions of the part of the annular metallic member 17 which remains after the cutting operation appear to be transversely wider than other portions. This will be the case in the majority of instances as a result of the distortion of the gear circle 16 which has been hereinbefore described. It is to be recalled, however, that the inner peripheral edge formed on the annular metallic member 17 by the cutting operation, and designated by reference character '70 in FIGURE 7 is truly circular in contiguration as a result of the use of the annular structure 82 shown in FIGURE 4 for determining the cutting line to be followed.

After the teeth 24 and the root or base portion of the gear circle 16 to which they are joined have been cut from the circle in the manner described, the inner peripheral surface 70 of the annular metallic member 17 is cleaned of slag and burrs, and the annular structure 82 is positioned inside the gear circle 16 and clamped in abutting contact with the inner peripheral surface 70 as illustrated in FIGURE 8. The annular structure 82 is then tack-welded over a length of two or three inches in eight staggered locations over the entire circumference of the circular meeting line between the annular structure 82 and the cutaway gear circle. This meeting line is designated byreference. character 72 Vin FIGURE 8. The tack welds are applied in staggered weld sequence with the second weld being applied 180 from the first weld, the third weld being applied 270 from the first weld, and the. fourth weld being applied directly across the circle from the thirdweld, and soV forth. This manner of welding -prevents distortion of the annular structure 82 of the preformed segments 50 fromv the true circular configuration, and better distributes vstresses induced in the metal by the welding heat. After a plurality, and `preferablyeight, tack Vwelds are'applied` in staggered sequence to the meeting line 72 at the top of the annular structure 82 and cutaway gear circle, the clamped-together structure shown in FIGURl-C 8 is turned over or inverted and the tack welding sequence is repeated on the other side thereof. The gear circle with the new segments and renewed teeth in place is then turned over again to the position illustrated in' FIGURE 8 and the welding is completed by fillet welding cornpletely around the groove formed between the beveled surface S6 vof the joined segments, and the surface 70 of the cutaway gear circle. The groove formed at the bottom of the members by the tapered surface 58 is also lled in with weld metal. Upon completion ofthe welding operation, the rebuilt gear circle is replaced in position on the earth-moving vehicle, and appears in transverse section as illustrated in FIGURE 9. 1V

The method of the present invention has the advantage of incorporating a new, truly circular, inner peripheral portion in the outer peripheral portion of an old gear circle 16 Aso as to povide new teeth of stronger, more durable metal. The portion of the gear circle 16 which is of greatest mechanical strength is the outer portion by reason ofthe inclusion therein of the tiange 32 and brace 36, and since this portion of the gear circle has already -sustained and undergone distortion, it is unlikely that the gear circle, provided it is reinstalled in its same relative position to the blade 22 which it occupied prior to removal, will undergo much, if any7 further` distortion. Thus, the new inner peripheral portion, including the new teeth 52, will resist distortion and remain of true circular configuration for most or all of the remaining operating life of the entire gear circle. The operation of replacing the worn and fractured teeth can .be accomplished by personnel of relatively little technical skill or training, and can be accomplished in less time than would be required to replace each of the replaced worn teeth in an individual manner. c f

Although a preferred method of practicing the present invention has been hereinbefore described, it will be understood that certain steps, procedures and materials described are to be considered equivalent to others not disclosed. Insofar, therefore, as any practice of the invention disclosed herein, whether authorized or unauthorized, employs steps and materials which are to any degree equivalent and analogous to the steps and materials herein disclosed, it is intended that such practices of the method of the invention shall be circumscribed and dominated by the appended claims except as such claims may be construed to be necessarily limited.

What is claimed is:

1. The method of replacing worn out and fractured teeth on a gear circle of the type having an annular rnetallic member enclosing a free, unobstructed space, said annular metallic member having radially inwardly extending gear teeth at the inner periphery thereof, said method comprising,

preforming a plurality of toothed, metallic arcuate segments each having a radius of curvature greater than the radius of curvature of a circle drawn through the points of connection of the teeth of said gear circle to said annular metallic member, each of said segments corresponding in maximum thickness to said gear circle, and each of said segments '10 having teeth of identical pitch and configuration to .those carried by said gear circle; joining said segments to each other in end-to-end relation to form an annular structure of precisely Vcircular configuration with the teeth of said segrnents 'extending radially inwardly; superimposing said annular structure on said gear circle in abutting contact with said annular-metallic member to derive an annular reference line coinciding with the line of intersection of the outer peripheral edfgeof said. annular structure with said annular metallic member; cutting through said annular metallic member on said annular reference line in a direction normal to the radii of said gear circle to remove from said gear circle the inner peripheral portion of said annular metallic member and the teeth carried thereby;

positioning said annular structure inside the outer peripheral portion of said gear circle in place of the removed inner peripheral portion thereof; and

securing said annular structure to said outer peripheral portion of said gear circle.

2. The method claimed in claim 1 wherein said metallic arcuate segments are preformed by casting using a harder, more durable metal than that used in the original teeth of the gear circle.

3. The method claimed in claim 1 wherein said gear circle is from four to seven feet in diameter and wherein said segmentsare each equivalent to an octant of the annular structure formed by joining said segments together.

4. A method claimed in claim 3 wherein said segments are joined to.V each other by placing said segments in end-toend relation upon an annular jig and welding said segments together. l

5. The method of replacing worn or fractured teeth on a metallic gear circle of the type having an annular metallic member enclosing a free, unobstructed space, said annular metallic member having radially inwardly extending gear teeth at the inner periphery thereof, and said gear circle being from four to seven feet in diameter and futher having annular brace means projecting from said annular metallic member and extending substantially normal to the radii of said gear circle and positioned between the inner periphery and outer periphery of said gear circle, said method -of replacement comprising:

preforming by casting a plurality of toothed, metallic arcuate segments each formed on the circumference of a common circle and each having a radius of curvature yshorter than the radial distance from the center of said gear circleV to the nearest portion of said annular brace means, and greater than the radial distance from the center of said gear circle to the base of the tooth of said gear circle farthest from the center thereof, said segments each corresponding in maximum thickness to the maximum thickness of said gear circle and having teeth of identical pitch and configuration to those carried by said gear circle;

joining said segments to each other in end-to-end relation to form an annular structure of precisely circular configuration with the teeth of said segments extending radially inwardly; superimposing said annular structure on said gear circle in abutting contact with said annular metallic member to derive an annular reference line coinciding with the meeting of the outer peripheral edge of said annular structure with said annular metallic member;

cutting through said annular metallic member along `said reference line in a direction normal to the radii of said gear circle to remove from said gear circle the inner peripheral portion of said annular metallic member and the teeth carried thereby;

positioning said annular structure inside the outer peripheral portion of said gear circle in place of the removed inner peripheral portion thereof; and

1 1 12 securing said annular structure to said outer peripheral 8. The method claimed in claim 7 wherein said segportion of said gear circle. `ments are joined to each other by placing said segments 6. The method claimed in claim 5 wherein said referin end-to-end relation upon an annular iig.' ence line is employed for cutting through said annular Y metallic member by using the outer peripheral edge of 5 References Cited by the Examiner said annular structure to guide a cutting torch in cutting UNITED STATES PATENTS through said annular metallic member along said refer- 814,342 3/1906 Atha 29 159 2 ence line- 3,083,585 4/1963 Dawe et a1 29-.401 X 7. The method claimed 1n claim 6 wherein said seg- 3,111,859 11 /1963 Mamme 74 .243

ments are each equivalent to an octant of the annular 10 structure formed by joining said segments together. WHITMORE A. WILTZ, Primary Examiner. 

1. THE METHOD OF REPLACING WORN OUT AND FRACTURED TEETH ON A GEAR CIRCLE OF THE TYPE HAVING AN ANNULAR METALLIC MEMBER ENCLOSING A FREE, UNOBSTRUCTED SPACE, SAID ANNULAR METALLIC MEMBER HAVING RADIALLY INWARDLY EXTENDING GEAR TEETH AT THE INNER PERIPHERY THEREOF, SAID METHOD COMPRISING, PREFORMING A PLURALITY OF TOOTHED, METALLIC ARCUATE SEGMENTS EACH HAVING A RADIUS OF CURVATURE GREATER THAN THE RADIUS OF CURVATURE OF A CIRCLE DRAWN THROUGH THE POINTS OF CONNECTION OF THE TEETH OF SAID GEAR CIRCLE TO SAID ANNULAR METALLIC MEMBER, EACH OF SAID SEGMENTS CORRESPONDING IN MAXIMUM THICKNESS TO SAID GEAR CIRCLE, AND EACH OF SAID SEGMENTS HAVING TEETH OF INDENTICAL PITCH AND CONFIGURATION TO THOSE CARRIED BY GEAR CIRCLE; JOINING SAID SEGMENTS TO EACH OTHER IN END-TO-END RELATION TO FORM AN ANNULAR STRUCTURE OF PRECISELY CIRCULAR CONFIGURATION WITH THE TEETH OF SAID SEGMENTS EXTENDING RADIALLY INWARDLY; SUPERIMPOSING SAID ANNULAR STRUCTURE ON SAID GEAR CIRCLE IN ABUTTING CONTACT WITH SAID ANNULAR METALLIC MEMBER TO DERIVE AN ANNULAR REFERENCE LINE COINCIDING WITH THE LINE OF INTERSECTION OF THE OUTER PERIPHERAL EDGE OF SAID ANNULAR STRUCTURE WITH SAID ANNULAR METALLIC MEMBER; CUTTING THROUGH SAID ANNULAR METALLIC MEMBER ON SAID ANNULAR REFERENCE LINE IN A DIRECTION NORMAL TO THE RADII OF SAID CIRCLE TO REMOVE FROM SAID GEAR CIRCLE THE INNER PERIPHERAL PORTION OF SAID ANNULAR METALLIC MEMBER AND THE TEETH CARRIED THEREBY; POSITIONING SAID ANNULAR STRUCTURE INSIDE THE OUTER PERIPHERAL PORTION OF SAID GEAR CIRCLE IN PLACE OF THE REMOVED INNER PERIPHERAL PORTION THEREOF; AND SECURING SAID ANNULAR STRUCTURE TO SAID OUTER PERIPHERAL PORTION OF SAID GEAR CIRCLE. 